1. Field of the Invention
This invention relates to the field of multiple-input bar code data stream decoding, and in particular, to multiple-input bar code data stream decoding from mixed types of bar code readers.
2. Description of Related Art
While devices exist to wedge, that is reconfigure, bar code data into the keyboard port of a computer, for example an IBM.RTM. computer, no devices exist which allow multiple bar code devices from different vendors to be connected simultaneously to a single bar code decoding processor. A technical problem stems from the fact that outputs from some bar code devices default to a logically high output level when idle, for example those available from Welch-Allyn, and some bar code devices default to a logically low output level when idle, for example those available from Hewlett Packard. This type of mixed format input data has precluded the logical AND'ing or OR'ing of outputs from these mixed-type sources of bar code data streams into a single data stream.
An RF wireless bar code scanner in U.S. Pat. No. 5,565,670 uses monostable multi vibrators OR'ed together as part of a data encoding scheme for the RF transmitter. A mechanism to print bar codes on the edges of photographic film in U.S. Pat. No. 5,274,396 uses a monostable multi vibrator to determine a forward or reverse movement of the film. A laser bar code scanner in U.S. Pat. No. 5,552,590 uses a single monostable multi vibrator in conjunction with a binary counter to determine the number of bar codes acquired during a single scan. A CCD type bar code scanner in U.S. Pat. No. 5,245,168 uses monostable multi vibrators to generate a CCD shift pulse signal and a LED control signal used to illuminate a bar code to be scanned. A bar code optical scanner in DE 3310201 uses monostable multi vibrators to control a bistable device to generate a single output signal from a dual element optical sensor.
None of the foregoing references, or any combination thereof, enables a plurality of bar code wands and slot readers of mixed-type to be permanently connected to a single bar code data stream decoder. More particularly, none teaches or suggests implementing a multiple-input mixed-type bar code data stream processor with retriggerable monostable multi vibrators for processing each bar code data stream.